The invention relates to oxygen sensors of the type incorporating a disc of stabilized solid electrolyte mounted in a ceramic tube of a non-electrolyte material. Two main problem areas which have arisen with such a construction relate to providing a hermetic seal which will hold the disc in the tube and attaching leads to the thin platinum electrodes on the faces of the disc. Although adequate solutions have been found individually for these problems, a substantial number of time consuming operations must be performed to produce a complete sensor assembly. For example, Shum et al U.S. Pat. No. 4,119,513 shows a sensor having an extremely uniform voltage response in which the platinum group metal leads to the platinum group metal electrodes extend the entire length of the tube, one inside and one outside, with the outside one extending over the sensing end of the tube to contact the sensing electrode. The disc is retained by a glass frit seal which has performed quite satisfactorily and is resistant to damage by thermal shock testing at temperatures of at least 1300.degree. F. Davis U.S. Pat. No. 4,123,344 discloses a disc type electrolyte which is retained by the shrinkage of a ceramic tube during firing. The disc is supported in a recess and has internal and external leads which include junctures of different materials and certain additional assembly parts. Generally, the small shrinkages obtained with most ceramics requires very close control of the outer diameter of the disc and the diameter of the counterbore in which the disc is mounted. Also, where glass frit seals are used, there can be virtually no defects in the mating surfaces if a gas-tight seal is to be achieved.